Navy Sonar Signals in Norwegian Waters : Behavioral Response Studies of Cetaceans to

Data on the responsiveness of cetaceans to sonar signals are lacking, with only a few species having been studied in relation to a few types of sonar signals, mostly SURTASS-LFA (Nowacek et al., 2007). Marine mammals have been shown to react to underwater noise (Richardson et al., 1995), and captive research has documented hearing (Schlundt et al., 2000) and stress (Romano et al., 2004) effects at high received levels. To reduce the risk of behavioral or physiological effects, a number of mitigation protocols have been developed, such as shut-down procedures when animals are sighted nearby. Another mitigation protocol is the ‘ramp-up’ protocol in which source levels are gradually increased prior to the onset of full-level transmissions. This protocol is thought to give nearby animals some time to move away before sonar transmissions reach maximum levels. However, it is unknown whether or not this protocol is actually effective.